def fib(x):
    if x == 0 or x == 1:
        return 1
    else:
        return fib(x - 1) + fib(x - 2)

###
print(fib(9))
#retun    fib(4)                     + fib(3)   3 +5
       #retun    fib(2)    +fib(1)
       #     fib(1) +fib(0)

#fib2 +fib1  3+2
#fib1 fib0 1+1

